The present invention relates to clamping devices. It finds particular application in conjunction with automated vises and will be described with particular reference thereto. It is to be appreciated, however, that the invention will find other applications in the machine tool, manufacturing, and other industries.
In the machine tool industry, parts are typically clamped in a vise or fixture and then subject to a metal removal or other manufacturing cycle. The accuracy with which the part is manufactured is dependent not only on the accuracy of the metal removal cycle, but also on the accuracy with which the part was positioned and held in the vise. Although the cutting cycles are nearly all automated, there is still a high level of manual loading and unloading of the raw and finished parts.
The loading and fixturing of parts for machining involves a wide diversity of vises, fixtures, and jigs with an equal diversity of loading techniques. A large portion of the clamping devices used as machine tool vises are capable of clamping a wide variety of parts. This facilitates a more rapid turn-around when changing the machine tool between machining runs for various parts.
Manual vises are in common use. Operators load the vise and manually torque the vise handle. First, this leads to repetitive motion injuries and operator fatigue. Operator fatigue, in turn, results in variable torquing of the vise handle. The variable torquing causes part distortion and poor tolerances in the machined part.
Some vises are hydraulically operated. However, hydraulic vises require large, cumbersome hydraulic hoses, expensive hydraulic power supplies, and control valves. The bulky hydraulics render hydraulic vises difficult to change-over to other types of parts. Moreover, hydraulic vises typically have hydraulic fluid leaks. When hydraulic fluid leaks, it contaminates the cutting fluids and the environment. Further, hydraulic vises have high maintenance costs and generate high noise levels.
Pneumatic vises also have shortcomings. First, pneumatic vises typically involve high noise levels, often exceeding OSHA limits. Moreover, pneumatic systems release oil mist into the air which creates the typical xe2x80x9cshop airxe2x80x9d smell. These oils contain carcinogens and are the subject of ongoing regulation efforts. Moreover, pneumatic systems require expensive compressors, filter/regulator packages, and maintenance. Finally, pneumatic vises have limited clamping forces.
In some automated machining operations, the vise and the workpiece are moved among one or more machining stations. Such movement is cumbersome with hydraulic and pneumatic power systems. Even though manual vises are not amenable to automated control and timing, the drawbacks of hydraulic and pneumatic vises are so great that manual vises are still in common usage.
The present invention contemplates a new and improved clamping device which overcomes the above problems and others.
In accordance with one aspect of the present invention, a clamping device is provided in which at least one of first and second clamping elements are movable between an open position for receiving a workpiece and a clamped position for holding the workpiece. A polymeric actuator controls movement of the clamping elements between the open and clamped positions. The polymeric actuator includes a housing that defines a polymer containing chamber. A polymer disposed in the chamber expands and contracts under heating and cooling. A driving element movably mounted in fluid communication with the chamber extends and retracts as the polymer expands and contracts. The driving element is connected with at least one of the clamping elements for driving the elements towards one of their open and clamped positions as the polymer expands.
In accordance with another aspect of the present invention, an electrically controlled actuator controls movement of the moveable clamping element(s) between the open and clamping positions.
In accordance with another aspect of the present invention, a machine tool system is provided. A plurality of clamping devices each include first and second clamping elements which selectively clamp workpieces. An electrochemical actuator is electrically controlled to move the gripping elements between open and clamping positions. At least one machine tool performs a material removal operation on the clamped workpiece. A computer controller is electrically connected with the machine tool and the clamping device for electrically controlling clamping and material removal operations.
In accordance with another aspect of the present invention, a polymeric actuator is provided. A generally circular bore is defined in a housing. An extensible and retractable drive element is slidably received in a drive element receiving port. A substantially circular bobbin is disposed eccentrically within the bore to define an annular polymer receiving chamber which is thicker toward the drive element receiving port and thinner opposite the drive element receiving port. A heat expansible polymer is disposed in the bore. A heater in thermal communication with the polymer selectively expands the polymer.
In accordance with another aspect of the present invention, a clamping method is provided. A clamping force biases the clamping element(s) toward the clamping position. A polymer is thermally expanded to move the clamping elements apart against the mechanical biased clamping force. A workpiece is placed between the clamping elements. The polymer is cooled and contracts such that the clamping elements are mechanically biased together to clamp the workpiece with the clamping force.
One advantage of the present invention is that it improves accuracy, creating uniform and repeatable clamping forces.
Another advantage of the present invention resides in shortened lead times with reduced loading and set up time.
Another advantage of the present invention is that it is electrically controlled. Hydraulic and pneumatic lines and associated overhead are eliminated.
Another advantage of the present invention is its safety to the operator. It is totally silent and does not leak hazardous fluids or mists into the environment.
Another advantage of the present invention resides in the simplified interface with automated machine tools.
Another advantage of the present invention resides in its simplicity.
Another advantage is that the clamping speed can be controlled at a rate slow enough to allow the operator to remove his/her fingers in time to avoid finger pinch situations, therefore improving operator safety.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.